US7646016B2 - Method for automated testing of the modulation transfer function in image sensors - Google Patents

Method for automated testing of the modulation transfer function in image sensors Download PDF

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US7646016B2
US7646016B2 US11/472,435 US47243506A US7646016B2 US 7646016 B2 US7646016 B2 US 7646016B2 US 47243506 A US47243506 A US 47243506A US 7646016 B2 US7646016 B2 US 7646016B2
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pixel cells
pixel
opaque material
imager
cells
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Kevin Duesman
Jeffrey Bruce
Peter P. Altice, Jr.
Moshe Reuven
Donald E. Robinson
Ed Jenkins
Joey Shah
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    • H01L23/522—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames including external interconnections consisting of a multilayer structure of conductive and insulating layers inseparably formed on the semiconductor body
    • H01L23/532—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames including external interconnections consisting of a multilayer structure of conductive and insulating layers inseparably formed on the semiconductor body characterised by the materials
    • H01L23/53204—Conductive materials
    • H01L23/53209—Conductive materials based on metals, e.g. alloys, metal silicides
    • H01L23/53228—Conductive materials based on metals, e.g. alloys, metal silicides the principal metal being copper
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    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
    • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
    • H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
    • H01L21/76801—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing
    • H01L21/76802—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing by forming openings in dielectrics
    • H01L21/76805—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing by forming openings in dielectrics the opening being a via or contact hole penetrating the underlying conductor
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/14603—Special geometry or disposition of pixel-elements, address-lines or gate-electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/1462—Coatings
    • H01L27/14623—Optical shielding
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/14625—Optical elements or arrangements associated with the device
    • H01L27/14627—Microlenses
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    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/14636—Interconnect structures
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    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14683—Processes or apparatus peculiar to the manufacture or treatment of these devices or parts thereof
    • H01L27/14687—Wafer level processing
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    • H01L31/02—Details
    • H01L31/0224—Electrodes
    • H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N17/00—Diagnosis, testing or measuring for television systems or their details
    • H04N17/002—Diagnosis, testing or measuring for television systems or their details for television cameras
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/28—Testing of electronic circuits, e.g. by signal tracer
    • G01R31/282—Testing of electronic circuits specially adapted for particular applications not provided for elsewhere
    • G01R31/2829—Testing of circuits in sensor or actuator systems
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    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/0001—Technical content checked by a classifier
    • H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Definitions

  • the present invention is directed to the measurement of the modulation transfer function of an imager, for example a CCD, CMOS or other imager.
  • CCDs charge coupled devices
  • photodiode arrays charge injection devices
  • hybrid focal plane arrays among others.
  • CCDs are often employed for image acquisition and enjoy a number of advantages, which makes it the incumbent technology, particularly for small size imaging applications.
  • CCDs are also capable of large formats with small pixel size and they employ low noise charge domain processing techniques.
  • CCD imagers also suffer from a number of disadvantages. For example, they are susceptible to radiation damage, they exhibit destructive read out over time, they require good light shielding to avoid image smear and they have high power dissipation for large arrays.
  • CCD arrays are difficult to integrate with CMOS processing in part due to a different processing technology and to their high capacitances, complicating the integration of on-chip drive and signal processing electronics with the CCD array. While there have been some attempts to integrate on-chip signal processing with the CCD array, these attempts have not been entirely successful. CCDs also must transfer an image by line charge transfers from pixel to pixel, requiring that the entire array be read out into a memory before individual pixels or groups of pixels can be accessed and processed. This takes time. CCDs may also suffer from incomplete charge transfer from pixel to pixel during charge transfer, which also results in image smear.
  • CMOS imagers Because of the inherent limitations in CCD technology, there is an interest in CMOS imagers for possible use as low cost imaging devices. A fully compatible CMOS sensor technology enabling a higher level of integration of an image array with associated processing circuits would be beneficial to many digital imaging applications.
  • CMOS imagers have a low voltage operation and low power consumption; CMOS imagers are compatible with integrated on-chip electronics (control logic and timing, image processing, and signal conditioning such as A/D conversion); CMOS imagers allow random access to the image data; and CMOS imagers have lower fabrication costs as compared with the conventional CCD since standard CMOS processing techniques can be used. Additionally, low power consumption is achieved for CMOS imagers because only one row of pixels at a time needs to be active during the readout and there is no charge transfer (and associated switching) from pixel to pixel during image acquisition. On-chip integration of electronics is particularly advantageous because of the potential to perform many signal conditioning functions in the digital domain (versus analog signal processing) as well as to achieve a reduction in system size and cost.
  • a CMOS imager circuit for example, includes a focal plane array of pixel cells; each cell includes a photosensor, for example, a photogate, photoconductor or a photodiode overlying a substrate for producing a photo-generated charge in a doped region of the substrate.
  • a typical readout circuit in each pixel cell includes at least a source follower transistor and a row select transistor for coupling the source follower transistor to a column output line; however other readout circuit configurations are possible.
  • the pixel cell also may have a floating diffusion node, connected to the gate of the source follower transistor. Charge generated by the photosensor is sent to the floating diffusion node.
  • the imager may also include a transistor for transferring charge from the photosensor to the floating diffusion node for charge conversion to a voltage and another transistor for resetting the floating diffusion node to a predetermined charge level prior to charge transference.
  • CMOS imager pixel cell for example, a four transistor (4T) pixel
  • all the active elements of a pixel cell perform the necessary functions of (1) photon to charge conversion; (2) transfer of charge to the floating diffusion node; (3) resetting the floating diffusion node to a known state before the transfer of charge to it; (4) selection of a pixel cell for readout; and (5) output and amplification of a signal representing a reset voltage and a pixel signal voltage based on the photo converted charges.
  • the so-called three transistor (3T) pixel circuit operates similarly, but connects the photosensor directly to the source follower.
  • CMOS imagers are generally known and are discussed, for example, in Nixon et al., “256 ⁇ 256 CMOS Active Pixel Sensor Camera-on-a-Chip,” IEEE Journal of Solid-State Circuits, Vol. 31(12) pp. 2046-2050, 1996; Mendis et al, “CMOS Active Pixel Image Sensors,” IEEE Transactions on Electron Devices, Vol. 41(3) pp. 452-453, 1994 as well as U.S. Pat. No. 5,708,263 and U.S. Pat. No. 5,471,515, all of which are herein incorporated by reference.
  • FIG. 1 illustrates a block diagram of a conventional CMOS imager device 308 having an array 200 of pixel cells, which may be 3T, 4T or pixels using other numbers of transistors.
  • Pixel cell array 200 comprises a plurality of pixel cells arranged in a predetermined number of columns and rows. The pixel cells of each row in array 200 are all turned on at the same time by a row select line, and the pixel cells of each column are selectively output by respective column select lines.
  • the row lines are selectively activated by the row driver 210 in response to row address decoder 220 and the column select lines are selectively activated by the column driver 260 in response to column address decoder 270 .
  • the CMOS imager is operated by the control circuit 250 that controls address decoders 220 , 270 for selecting the appropriate row and column lines for pixel operation and readout, and row and column driver circuitry 210 , 260 that apply driving voltage to the drive transistors of the selected row and column lines.
  • the pixel column signals which typically each include a pixel reset signal, V rst and a pixel image signal, V sig , for a pixel cell selectively connected to a column line are read by a sample and hold circuit 261 associated with the column driver 260 and are subtracted by amplifier 262 to form a differential signal V rst -V sig for each pixel cell which is amplified and then digitized by analog to digital converter 275 .
  • the analog to digital converter 275 converts the received analog pixel signals to digital signals, which are fed to an image processor 280 to form a digital image.
  • CMOS imager The operation of the charge collection of the CMOS imager is known in the art and is described in several publications such as Mendis et al., “Progress in CMOS Active Pixel Image Sensors,” SPIE Vol. 2172, pp. 19-29 1994; Mendis et al., “CMOS Active Pixel Image Sensors for Highly Integrated Imaging Systems,” IEEE Journal of Solid State Circuits, Vol. 32(2), 1997; and Eric R, Fossum, “CMOS Image Sensors: Electronic Camera on a Chip,” IEDM Vol. 95 pages 17-25 (1995) as well as other publications. These references are incorporated herein by reference.
  • Imager arrays are typically tested to determine the signal to noise ratio for each pixel cell or a row or column of pixel cells.
  • pixel cells receive an input signal
  • some of the input signal is also received by adjacent pixel cells.
  • the spread of an input signal to adjacent pixel cells causes the adjacent pixel cells to incorrectly sense light intensity from a received image. Accordingly, the amount of such adjacent pixel cell spread is an important parameter to consider in the design and fabrication of a pixel cell array.
  • the amount of spread of an input signal to adjacent pixel cells, carrier diffusion (electrical crosstalk) can be determined by the modulation transfer function (MTF) of the imager array, which is an effective measurement of the sharpness and spatial resolution for the imager array.
  • MTF modulation transfer function
  • the MTF for an imager array can also be calculated using measurements of input signal reflection, interference or scattering as the input signal passes through various layers, i.e. metal, microlens, etc., of the imager array (optical crosstalk). This MTF is a value of interest for imager arrays in general, including both CCD and CMOS arrays, among others.
  • A the pixel value on the light side of the edge
  • D the pixel value on the dark side away from the edge.
  • This formula compares the degraded contrast at the light/dark edge to the maximum contrast of the sensor (totally dark signal—totally bright or saturated signal).
  • the test typically uses an entire column of pixel cells, which are averaged, instead of an individual pixel cell in order to avoid erroneous aberrations of individual pixel cells.
  • the present invention provides an automated method for measuring the MTF of a pixel cell array, for example, a pixel cell array of a CMOS imager.
  • a mask consisting of an opaque material, for example, a metal is placed over selected columns and rows of the imager array during fabrication.
  • an automated process such as a probe process, which tests the imager array at the wafer level for failing components, or final testing where packaged parts are tested, light is uniformly shone over the pixel cells on either side of the mask edge.
  • the amount of pixel signal that flows from the unmasked pixel cells to the pixel cells that are masked can then be measured and the MTF can be determined.
  • the mask can be fabricated as a mask that is used to separate the pixel cells of an array used for image acquisition from those used as merely dark pixels (not used for image acquisition), or can be fabricated as an opening in such a mask that is provided in a dark pixel area.
  • FIG. 1 is a block diagram of a conventional CMOS imager
  • FIG. 2 is a block diagram of a CMOS pixel sensor under test according to a first exemplary embodiment of the invention
  • FIG. 2A is an illustration of electrical crosstalk and optical crosstalk
  • FIG. 3 is a block diagram of a CMOS pixel sensor under test according to a second exemplary embodiment of the invention.
  • FIG. 4 is a schematic block diagram of a test system that includes software for automated testing of the modulation transfer function in a CMOS imager;
  • FIG. 5 is a flowchart illustrating an operational flow of FIGS. 2 and 3 block diagrams.
  • the present invention provides an automated method for measuring the modulation transfer function (MTF) in digital imagers by measuring the amount of light received by masked and unmasked pixel cells of an imager array and calculating the MTF (crosstalk) of the imager.
  • MTF modulation transfer function
  • the invention has applicability to any type of digital imager, including but not limited to CCD and CMOS imagers, the principles of the invention will be described below in connection with a CMOS imager.
  • FIG. 2 depicts a block diagram of a CMOS pixel sensor test system 500 in accordance with a first exemplary embodiment of the invention.
  • An opaque mask 202 for example, a metal mask, is formed on an edge of pixel cell array 200 and masks a predetermined number (e.g., 12) of rows of pixel cells at the top and bottom edges of the pixel cell array 200 .
  • Opaque mask 202 is permanently formed on the pixel array 200 .
  • the mask masks a predetermined number (e.g., 16) of columns of pixel cells at the left side and right side edges of the pixel cell array 200 .
  • Mask 202 is formed on the pixel cell array during fabrication of the CMOS imager.
  • the mask 202 may be formed on the pixel cell array 200 using photolithography and dry/wet etching, or any other method.
  • a color filter 205 is depicted as covering the pixel cells of pixel cell array 200 enclosed within the opaque mask 202 .
  • the use of color filters may be desirable when testing with different colors (e.g., wavelengths) of light, but are not required to practice the invention.
  • light from light source 400 which is less than the saturation light intensity, is uniformly shone over the entire pixel cell array 200 during post fabrication probe testing.
  • the test light should be below the intensity that would cause pixel saturation since pixel saturation may cause excessive electrons on the light side to bloom into the dark side, which would distort the MTF measurement.
  • the response is measured by reading out and measuring pixel signals on either side of a mask edge. Measurements are taken of the pixel signals on both sides of the border between the masked and unmasked portion of pixel cell array 200 . Measurements of multiple pixel signals on both sides of the border may also be utilized to avoid an erroneous result due to an aberration of an individual pixel cell and provide statistical significance to the measurement.
  • the signals of the multiple pixel cells on the same side of the border are averaged. In this border region, rather than a sharp black to white transition, a gray region is expected due to the effects of MTF.
  • the crosstalk can be measured at the border region and used to determine the MTF of the CMOS imager by techniques known in the art. It should be noted that this measurement is not limited to using pixels at all four edges of the opaque mask 202 , but rather may be performed on any part of the border between the pixel cells covered by the opaque mask 202 , and the pixel cells not covered by the opaque mask 202 .
  • the light used to measure MTF is collimated so that crosstalk being measured at the border between the masked and unmasked pixel cells is limited to electrical crosstalk, while minimizing optical crosstalk, illustrated in FIG. 2A .
  • the light used at probe is generally not collimated light.
  • an initial test is performed on a pixel cell array utilizing collimated light to form a standard, or control, test result. It should be noted, however, that this test standard would be useful only for a particular batch of image sensors or for multiple batches depending on the degree with which the MTF changes between batches. The pixel cell array is then tested during probe, or some other automated process, using light that is not collimated.
  • test results between the test using non-collimated light and the standard are then compared. If the difference between the two tests is negligible, the measurement of MTF utilizing non-collimated light is deemed reliable. However, if the difference between the two tests is not negligible, a correlation table or scaling factor may be employed to match the MTF calculated using non-collimated light to the standard test result using collimated light. Acceptable deviations can be established by the operator depending on the specific application, test conditions, etc. Once the MTF is measured, correction of the test using non-collimated light may then be performed. As is known in the art, the correction algorithm involves performing an inverse MTF transform on the image.
  • FIG. 3 illustrates a block diagram of a CMOS pixel sensor test system 500 in accordance with a second exemplary embodiment of the invention.
  • This embodiment is similar to the previous embodiment; however, a permanent opening 204 is created in mask 202 .
  • a window comprising 8 rows by 2 columns is provided in the mask 202 , exposing pixel cells generally not used in pixel cell array 200 since these pixel cells are normally covered by the opaque mask 202 .
  • Light is uniformly shone over the entire pixel cell array 200 during probe by light source 400 , as described above.
  • a measurement of the pixel cells on both sides of the border between the masked pixel cells and the pixel cells within the 8 ⁇ 2 unmasked portion 204 of the pixel cell array 200 is then taken to determine the MTF.
  • FIG. 4 depicts a processor system 300 configured to test the modulation transfer function of an imager pixel cell array under test in the FIGS. 2 and 3 test systems.
  • System 300 includes central processing unit (CPU) 302 that communicates with various devices over bus 304 . Some of the devices connected to bus 304 provide communication into and out of system 300 , illustratively including input/output (I/O) device 306 and pixel sensor test system 500 , as illustrated in FIGS. 2 and 3 .
  • Pixel sensor test system 500 forwards to processor system 300 measurements taken during probe, which include measurements taken for calculating MTF as described above in connection with FIGS. 2 and 3 .
  • CPU 302 then receives these measurements and calculates MIT for the pixel sensors.
  • RAM random access memory
  • hard drive 312 hard drive 312
  • peripheral memory devices such as floppy disk drive 314 and compact disk (CD) drive 316 .
  • Any one of the many storage mediums capable of being read by CPU 302 may store the test process used during operation of the FIGS. 2 and 3 pixel sensor test systems 500 .
  • the test process may be a modified version of the existing probe test software.
  • FIG. 5 depicts a flowchart illustrating an operational flow of an automated test process for measuring MTF on an imager array.
  • light is shone from light source 400 onto the masked pixel array 200 .
  • signals generated by the masked pixel cells that are adjacent to the border between the masked and unmasked pixel cells are measured.
  • signals generated by the unmasked pixel cells that are adjacent to the border between masked and unmasked pixel cells are measured.
  • the CPU 302 calculates MTF based on the measurements taken.

Abstract

A method for automatically measuring the modulation transfer function of an imager is disclosed. A opaque mask is placed over selected columns and rows of the imager during fabrication. In the course of an automated process, photons are uniformly shone over the image sensor. The amount of the input signal that flows from the unmasked pixel cells to the masked pixel cells can then be measured and the modulation transfer function can be determined.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a divisional of U.S. patent application Ser. No. 10/663,709, filed Sep. 17, 2003 now U.S. Pat. 7,215,361, the entire contents of which are herewith incorporated by reference in its entirety.
FIELD OF THE INVENTION
The present invention is directed to the measurement of the modulation transfer function of an imager, for example a CCD, CMOS or other imager.
BACKGROUND OF THE INVENTION
There are a number of different types of semiconductor-based imagers, including charge coupled devices (CCDs), photodiode arrays, charge injection devices and hybrid focal plane arrays, among others. CCDs are often employed for image acquisition and enjoy a number of advantages, which makes it the incumbent technology, particularly for small size imaging applications. CCDs are also capable of large formats with small pixel size and they employ low noise charge domain processing techniques. However, CCD imagers also suffer from a number of disadvantages. For example, they are susceptible to radiation damage, they exhibit destructive read out over time, they require good light shielding to avoid image smear and they have high power dissipation for large arrays. Additionally, while offering high performance, CCD arrays are difficult to integrate with CMOS processing in part due to a different processing technology and to their high capacitances, complicating the integration of on-chip drive and signal processing electronics with the CCD array. While there have been some attempts to integrate on-chip signal processing with the CCD array, these attempts have not been entirely successful. CCDs also must transfer an image by line charge transfers from pixel to pixel, requiring that the entire array be read out into a memory before individual pixels or groups of pixels can be accessed and processed. This takes time. CCDs may also suffer from incomplete charge transfer from pixel to pixel during charge transfer, which also results in image smear.
Because of the inherent limitations in CCD technology, there is an interest in CMOS imagers for possible use as low cost imaging devices. A fully compatible CMOS sensor technology enabling a higher level of integration of an image array with associated processing circuits would be beneficial to many digital imaging applications.
The advantages of CMOS imagers over CCD imagers are that CMOS imagers have a low voltage operation and low power consumption; CMOS imagers are compatible with integrated on-chip electronics (control logic and timing, image processing, and signal conditioning such as A/D conversion); CMOS imagers allow random access to the image data; and CMOS imagers have lower fabrication costs as compared with the conventional CCD since standard CMOS processing techniques can be used. Additionally, low power consumption is achieved for CMOS imagers because only one row of pixels at a time needs to be active during the readout and there is no charge transfer (and associated switching) from pixel to pixel during image acquisition. On-chip integration of electronics is particularly advantageous because of the potential to perform many signal conditioning functions in the digital domain (versus analog signal processing) as well as to achieve a reduction in system size and cost.
A CMOS imager circuit, for example, includes a focal plane array of pixel cells; each cell includes a photosensor, for example, a photogate, photoconductor or a photodiode overlying a substrate for producing a photo-generated charge in a doped region of the substrate. A typical readout circuit in each pixel cell includes at least a source follower transistor and a row select transistor for coupling the source follower transistor to a column output line; however other readout circuit configurations are possible. The pixel cell also may have a floating diffusion node, connected to the gate of the source follower transistor. Charge generated by the photosensor is sent to the floating diffusion node. The imager may also include a transistor for transferring charge from the photosensor to the floating diffusion node for charge conversion to a voltage and another transistor for resetting the floating diffusion node to a predetermined charge level prior to charge transference.
In a CMOS imager pixel cell, for example, a four transistor (4T) pixel, all the active elements of a pixel cell perform the necessary functions of (1) photon to charge conversion; (2) transfer of charge to the floating diffusion node; (3) resetting the floating diffusion node to a known state before the transfer of charge to it; (4) selection of a pixel cell for readout; and (5) output and amplification of a signal representing a reset voltage and a pixel signal voltage based on the photo converted charges. The so-called three transistor (3T) pixel circuit operates similarly, but connects the photosensor directly to the source follower.
CMOS imagers are generally known and are discussed, for example, in Nixon et al., “256×256 CMOS Active Pixel Sensor Camera-on-a-Chip,” IEEE Journal of Solid-State Circuits, Vol. 31(12) pp. 2046-2050, 1996; Mendis et al, “CMOS Active Pixel Image Sensors,” IEEE Transactions on Electron Devices, Vol. 41(3) pp. 452-453, 1994 as well as U.S. Pat. No. 5,708,263 and U.S. Pat. No. 5,471,515, all of which are herein incorporated by reference.
FIG. 1 illustrates a block diagram of a conventional CMOS imager device 308 having an array 200 of pixel cells, which may be 3T, 4T or pixels using other numbers of transistors. Pixel cell array 200 comprises a plurality of pixel cells arranged in a predetermined number of columns and rows. The pixel cells of each row in array 200 are all turned on at the same time by a row select line, and the pixel cells of each column are selectively output by respective column select lines. The row lines are selectively activated by the row driver 210 in response to row address decoder 220 and the column select lines are selectively activated by the column driver 260 in response to column address decoder 270. The CMOS imager is operated by the control circuit 250 that controls address decoders 220, 270 for selecting the appropriate row and column lines for pixel operation and readout, and row and column driver circuitry 210, 260 that apply driving voltage to the drive transistors of the selected row and column lines. The pixel column signals, which typically each include a pixel reset signal, Vrst and a pixel image signal, Vsig, for a pixel cell selectively connected to a column line are read by a sample and hold circuit 261 associated with the column driver 260 and are subtracted by amplifier 262 to form a differential signal Vrst-Vsig for each pixel cell which is amplified and then digitized by analog to digital converter 275. The analog to digital converter 275 converts the received analog pixel signals to digital signals, which are fed to an image processor 280 to form a digital image.
The operation of the charge collection of the CMOS imager is known in the art and is described in several publications such as Mendis et al., “Progress in CMOS Active Pixel Image Sensors,” SPIE Vol. 2172, pp. 19-29 1994; Mendis et al., “CMOS Active Pixel Image Sensors for Highly Integrated Imaging Systems,” IEEE Journal of Solid State Circuits, Vol. 32(2), 1997; and Eric R, Fossum, “CMOS Image Sensors: Electronic Camera on a Chip,” IEDM Vol. 95 pages 17-25 (1995) as well as other publications. These references are incorporated herein by reference.
Imager arrays are typically tested to determine the signal to noise ratio for each pixel cell or a row or column of pixel cells. In addition, when pixel cells receive an input signal, some of the input signal is also received by adjacent pixel cells. The spread of an input signal to adjacent pixel cells causes the adjacent pixel cells to incorrectly sense light intensity from a received image. Accordingly, the amount of such adjacent pixel cell spread is an important parameter to consider in the design and fabrication of a pixel cell array. The amount of spread of an input signal to adjacent pixel cells, carrier diffusion (electrical crosstalk), can be determined by the modulation transfer function (MTF) of the imager array, which is an effective measurement of the sharpness and spatial resolution for the imager array. The greater the carrier diffusion, the lower the sharpness and resolution for the imager array. The MTF for an imager array can also be calculated using measurements of input signal reflection, interference or scattering as the input signal passes through various layers, i.e. metal, microlens, etc., of the imager array (optical crosstalk). This MTF is a value of interest for imager arrays in general, including both CCD and CMOS arrays, among others.
A current method for testing MTF for image sensor arrays involves measuring the edge response of the imager array by applying an image signal to the image array that has a dark image section adjacent to a light image section. The edge between the dark and light sections is lined up exactly between two adjacent pixel columns in the imager array and the MTF is calculated as follows:
MTF=(A−B)/(C−D)
where A=the pixel value on the light side of the edge;
B=the pixel value on the dark side of the edge;
C=the pixel value on the light side away from the edge; and
D=the pixel value on the dark side away from the edge.
This formula compares the degraded contrast at the light/dark edge to the maximum contrast of the sensor (totally dark signal—totally bright or saturated signal). The test typically uses an entire column of pixel cells, which are averaged, instead of an individual pixel cell in order to avoid erroneous aberrations of individual pixel cells.
It is difficult to automate the above-described testing method for several reasons. Such testing is generally performed during probe, where various tests are automatically performed to determine acceptable and failing parts. During probe the alignment of the dark and light edge of an input image exactly between two adjacent columns of pixel cells of an imager array is complex since, for example, rotation of the die and input image have to be the same. Accordingly, there is a need and desire for a better method of measuring the MTF of pixel array imagers.
BRIEF SUMMARY OF THE INVENTION
The present invention provides an automated method for measuring the MTF of a pixel cell array, for example, a pixel cell array of a CMOS imager. A mask consisting of an opaque material, for example, a metal is placed over selected columns and rows of the imager array during fabrication. During an automated process such as a probe process, which tests the imager array at the wafer level for failing components, or final testing where packaged parts are tested, light is uniformly shone over the pixel cells on either side of the mask edge. The amount of pixel signal that flows from the unmasked pixel cells to the pixel cells that are masked can then be measured and the MTF can be determined. The mask can be fabricated as a mask that is used to separate the pixel cells of an array used for image acquisition from those used as merely dark pixels (not used for image acquisition), or can be fabricated as an opening in such a mask that is provided in a dark pixel area.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other features and advantages of the invention will become more apparent from the detailed description of the exemplary embodiments of the invention given below in connection with the accompanying drawings.
FIG. 1 is a block diagram of a conventional CMOS imager;
FIG. 2 is a block diagram of a CMOS pixel sensor under test according to a first exemplary embodiment of the invention;
FIG. 2A is an illustration of electrical crosstalk and optical crosstalk;
FIG. 3 is a block diagram of a CMOS pixel sensor under test according to a second exemplary embodiment of the invention;
FIG. 4 is a schematic block diagram of a test system that includes software for automated testing of the modulation transfer function in a CMOS imager; and
FIG. 5 is a flowchart illustrating an operational flow of FIGS. 2 and 3 block diagrams.
 DETAILED DESCRIPTION OF THE INVENTION
In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those of ordinary skill in the art to make and use the invention, and it is to be understood that structural, logical or procedural changes may be made to the specific embodiments disclosed without departing from the spirit and scope of the present invention.
The present invention provides an automated method for measuring the modulation transfer function (MTF) in digital imagers by measuring the amount of light received by masked and unmasked pixel cells of an imager array and calculating the MTF (crosstalk) of the imager. Although the invention has applicability to any type of digital imager, including but not limited to CCD and CMOS imagers, the principles of the invention will be described below in connection with a CMOS imager.
FIG. 2 depicts a block diagram of a CMOS pixel sensor test system 500 in accordance with a first exemplary embodiment of the invention. An opaque mask 202, for example, a metal mask, is formed on an edge of pixel cell array 200 and masks a predetermined number (e.g., 12) of rows of pixel cells at the top and bottom edges of the pixel cell array 200. Opaque mask 202 is permanently formed on the pixel array 200. In addition, the mask masks a predetermined number (e.g., 16) of columns of pixel cells at the left side and right side edges of the pixel cell array 200. Mask 202 is formed on the pixel cell array during fabrication of the CMOS imager. The mask 202 may be formed on the pixel cell array 200 using photolithography and dry/wet etching, or any other method. In addition, a color filter 205 is depicted as covering the pixel cells of pixel cell array 200 enclosed within the opaque mask 202. The use of color filters may be desirable when testing with different colors (e.g., wavelengths) of light, but are not required to practice the invention.
Once the mask 202 is formed on the pixel cell array 200 during fabrication, light from light source 400, which is less than the saturation light intensity, is uniformly shone over the entire pixel cell array 200 during post fabrication probe testing. The test light should be below the intensity that would cause pixel saturation since pixel saturation may cause excessive electrons on the light side to bloom into the dark side, which would distort the MTF measurement.
The response is measured by reading out and measuring pixel signals on either side of a mask edge. Measurements are taken of the pixel signals on both sides of the border between the masked and unmasked portion of pixel cell array 200. Measurements of multiple pixel signals on both sides of the border may also be utilized to avoid an erroneous result due to an aberration of an individual pixel cell and provide statistical significance to the measurement. When measuring multiple pixel cells on a particular side of the border, the signals of the multiple pixel cells on the same side of the border are averaged. In this border region, rather than a sharp black to white transition, a gray region is expected due to the effects of MTF. The crosstalk can be measured at the border region and used to determine the MTF of the CMOS imager by techniques known in the art. It should be noted that this measurement is not limited to using pixels at all four edges of the opaque mask 202, but rather may be performed on any part of the border between the pixel cells covered by the opaque mask 202, and the pixel cells not covered by the opaque mask 202.
Ideally, the light used to measure MTF is collimated so that crosstalk being measured at the border between the masked and unmasked pixel cells is limited to electrical crosstalk, while minimizing optical crosstalk, illustrated in FIG. 2A. However, the light used at probe is generally not collimated light. For best results, an initial test is performed on a pixel cell array utilizing collimated light to form a standard, or control, test result. It should be noted, however, that this test standard would be useful only for a particular batch of image sensors or for multiple batches depending on the degree with which the MTF changes between batches. The pixel cell array is then tested during probe, or some other automated process, using light that is not collimated.
The test results between the test using non-collimated light and the standard are then compared. If the difference between the two tests is negligible, the measurement of MTF utilizing non-collimated light is deemed reliable. However, if the difference between the two tests is not negligible, a correlation table or scaling factor may be employed to match the MTF calculated using non-collimated light to the standard test result using collimated light. Acceptable deviations can be established by the operator depending on the specific application, test conditions, etc. Once the MTF is measured, correction of the test using non-collimated light may then be performed. As is known in the art, the correction algorithm involves performing an inverse MTF transform on the image.
FIG. 3 illustrates a block diagram of a CMOS pixel sensor test system 500 in accordance with a second exemplary embodiment of the invention. This embodiment is similar to the previous embodiment; however, a permanent opening 204 is created in mask 202. For example, a window comprising 8 rows by 2 columns is provided in the mask 202, exposing pixel cells generally not used in pixel cell array 200 since these pixel cells are normally covered by the opaque mask 202.
Light is uniformly shone over the entire pixel cell array 200 during probe by light source 400, as described above. A measurement of the pixel cells on both sides of the border between the masked pixel cells and the pixel cells within the 8×2 unmasked portion 204 of the pixel cell array 200 is then taken to determine the MTF.
It should be noted that in those instances in which a color filter 205 is used, since the color filter covers only pixel cell array 200, the test performed in the, e.g., 8×2 section of the unmasked portion, as illustrated in FIG. 3, would be a black and white test. The measurement of the MTF using this unmasked area would tend to be a truer representation of the pixel cell array's resolution since there would be no color filter to create distortion of the incident light.
FIG. 4 depicts a processor system 300 configured to test the modulation transfer function of an imager pixel cell array under test in the FIGS. 2 and 3 test systems. System 300 includes central processing unit (CPU) 302 that communicates with various devices over bus 304. Some of the devices connected to bus 304 provide communication into and out of system 300, illustratively including input/output (I/O) device 306 and pixel sensor test system 500, as illustrated in FIGS. 2 and 3. Pixel sensor test system 500 forwards to processor system 300 measurements taken during probe, which include measurements taken for calculating MTF as described above in connection with FIGS. 2 and 3. CPU 302 then receives these measurements and calculates MIT for the pixel sensors. Other devices depicted as being connected to bus 304, including for example, random access memory (RAM) 310, hard drive 312, and one or more peripheral memory devices such as floppy disk drive 314 and compact disk (CD) drive 316. Any one of the many storage mediums capable of being read by CPU 302, including but not limited to floppy disk 395 and compact disk 390, may store the test process used during operation of the FIGS. 2 and 3 pixel sensor test systems 500. The test process may be a modified version of the existing probe test software.
FIG. 5 depicts a flowchart illustrating an operational flow of an automated test process for measuring MTF on an imager array. At segment 5510, light is shone from light source 400 onto the masked pixel array 200. At segment 5520, signals generated by the masked pixel cells that are adjacent to the border between the masked and unmasked pixel cells are measured. At segment 5530, signals generated by the unmasked pixel cells that are adjacent to the border between masked and unmasked pixel cells are measured. At segment 5540, the CPU 302 calculates MTF based on the measurements taken.
While the invention has been described and illustrated with reference to specific exemplary embodiments, it should be understood that many modifications and substitutions could be made without departing from the spirit and scope of the invention. For example, although a mask 202 having specific exemplary dimensions is described in connection with the invention, it should be readily apparent that a mask of any size may be used. Further, while specific test parameters and values have been identified, practicing the invention is not limited thereto. Accordingly, the invention is not to be considered as limited by the foregoing description but is only limited by the scope of the appended claims.

Claims (12)

1. An apparatus for testing a modulation transfer function of an imager comprising photosensitive cells, the apparatus comprising:
an opaque material permanently blocking a plurality of rows and columns of photosensitive cells; and
an opening in the opaque material, wherein an edge of said opening is aligned between a row or column of image-acquisition photosensitive cells of the imager and a respective adjacent row or column of the photosensitive cells permanently blocked by the opaque material.
2. The apparatus of claim 1, wherein the apparatus is configured to measure an output from said adjacent row or column of photosensitive cells for calculation of the modulation transfer function.
3. The apparatus of claim 2, wherein said measurement occurs during an automated testing process.
4. The apparatus of claim 1, wherein a plurality of photosensitive cells blocked by said opaque material are configured to be measured and a plurality of image-acquisition photosensitive cells, adjacent to said blocked photosensitive cells, are configured to be measured.
5. The apparatus of claim 4, wherein said measurements taken from said plurality of photosensitive cells blocked by said opaque material are averaged and said plurality of image-acquisition photosensitive cells, adjacent to said blocked photosensitive cells, are averaged.
6. An imager comprising:
an array of pixel cells arranged in a plurality of rows and columns;
an opaque material permanently formed over a plurality of rows and columns, the opaque material having an opening, wherein an edge of said opening is aligned between a row or column of image-acquisition pixel cells and a respective adjacent row or column of pixel cells residing below the opaque material; and
a circuit configured to calculate a modulation transfer function for the imager.
7. The imager of claim 6, wherein the opaque material is formed over a predetermined number of columns of pixel cells on the left and right edges of the array of pixel cells.
8. The imager of claim 6, wherein the opaque material is formed over a predetermined number of rows of pixel cells on the top and bottom edges of the array of pixel cells.
9. The imager of claim 6, wherein said plurality of pixel cells blocked by said opaque material are configured to be measured and averaged and said plurality of image-acquisition pixel cells, adjacent to said blocked pixel cells, are configured to be measured and averaged to calculate the modulation transfer function.
10. An imager comprising:
an array of pixel cells arranged in a plurality of rows and columns, the array of pixel cells comprising a first and second array section;
an opaque material permanently formed on at least a portion of the second array section, the opaque material having a window where an edge of said window is aligned between a row or column of first-section pixel cells and a respective adjacent row or column of second-section pixel cells under the opaque material; and
a circuit configured to calculate a modulation transfer function of the imager.
11. The image of claim 10, wherein the second array section is not used to collect data representing an image.
12. The image of claim 10, wherein measurements are taken in the second array section, the measurements from said second-section plurality of pixel cells blocked by said opaque material are averaged and said plurality of first-section pixel cells not blocked by said opaque material, adjacent to said blocked pixel cells, are averaged to calculate the modulation transfer function.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10267684B1 (en) 2017-04-11 2019-04-23 United States Of America As Represented By The Secretary Of The Air Force Device, system, and technique for characterizing a focal plane array modulation transfer function

Families Citing this family (63)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6879340B1 (en) * 1998-08-19 2005-04-12 Micron Technology Inc. CMOS imager with integrated non-volatile memory
US7561194B1 (en) * 2003-10-17 2009-07-14 Eastman Kodak Company Charge diffusion crosstalk reduction for image sensors
JP4445327B2 (en) * 2004-05-21 2010-04-07 大塚電子株式会社 Display evaluation method and apparatus
US7400352B1 (en) * 2004-05-26 2008-07-15 Eastman Kodak Company Method of estimating electrical cross talk in an array of imaging cells
US7193289B2 (en) * 2004-11-30 2007-03-20 International Business Machines Corporation Damascene copper wiring image sensor
US7592645B2 (en) 2004-12-08 2009-09-22 Canon Kabushiki Kaisha Photoelectric conversion device and method for producing photoelectric conversion device
US7342268B2 (en) * 2004-12-23 2008-03-11 International Business Machines Corporation CMOS imager with Cu wiring and method of eliminating high reflectivity interfaces therefrom
KR100719341B1 (en) * 2005-01-25 2007-05-17 삼성전자주식회사 Image sensor and method of fabricating the same
US7935994B2 (en) * 2005-02-24 2011-05-03 Taiwan Semiconductor Manufacturing Company, Ltd. Light shield for CMOS imager
US20060198008A1 (en) * 2005-03-07 2006-09-07 Micron Technology, Inc. Formation of micro lens by using flowable oxide deposition
US7675096B2 (en) * 2005-03-30 2010-03-09 Fujifilm Corporation Solid-state image pickup element and method of producing the same
JP4388909B2 (en) * 2005-04-25 2009-12-24 イーストマン コダック カンパニー Pixel defect correction device
US7423668B2 (en) * 2005-07-11 2008-09-09 Eastman Kodak Company On-chip block balancing structure and method for multiple output image sensors
KR100772250B1 (en) * 2005-12-27 2007-11-01 동부일렉트로닉스 주식회사 Method for forming metal layer in semiconductor damascene manufacturing process
KR100731128B1 (en) * 2005-12-28 2007-06-22 동부일렉트로닉스 주식회사 Method for manufacturing cmos image sensor
US20070241418A1 (en) * 2006-04-13 2007-10-18 Ming-I Wang Image sensing device and fabrication method thereof
US7803647B2 (en) * 2007-02-08 2010-09-28 Taiwan Semiconductor Manufacturing Company, Ltd. Optical transmission improvement on multi-dielectric structure in advance CMOS imager
KR100851495B1 (en) 2007-05-14 2008-08-08 매그나칩 반도체 유한회사 Small pixel for image sensors with jfet and vertically integrated reset diodes
KR100851494B1 (en) * 2007-05-14 2008-08-08 매그나칩 반도체 유한회사 Small pixel for cmos image sensors with vertically integrated set and reset diodes
US7825019B2 (en) * 2007-09-28 2010-11-02 International Business Machines Corporation Structures and methods for reduction of parasitic capacitances in semiconductor integrated circuits
KR20090037004A (en) * 2007-10-11 2009-04-15 주식회사 동부하이텍 Image sensor and method for manufacturing thereof
JP4803156B2 (en) * 2007-10-16 2011-10-26 ソニー株式会社 SIGNAL PROCESSING DEVICE FOR SOLID-STATE IMAGING ELEMENT, IMAGING DEVICE HAVING SIGNAL PROCESSING DEVICE, SIGNAL PROCESSING METHOD, AND PROGRAM
KR100856948B1 (en) * 2007-12-27 2008-09-04 주식회사 동부하이텍 Method for manufacturing of image sensor
TWI377508B (en) * 2008-01-17 2012-11-21 Asia Optical Co Inc Image pickup methods and image pickup systems using the same
US8319301B2 (en) * 2008-02-11 2012-11-27 Omnivision Technologies, Inc. Self-aligned filter for an image sensor
KR101251028B1 (en) 2008-04-26 2013-04-04 광주과학기술원 Optical connection structure and method for fabricating the same
WO2009131426A2 (en) * 2008-04-26 2009-10-29 광주과학기술원 Optical wiring structure and a production method therefor
KR101233311B1 (en) 2009-04-24 2013-02-14 광주과학기술원 Optical interconnection structure and method for fabricating the same
US8003425B2 (en) * 2008-05-14 2011-08-23 International Business Machines Corporation Methods for forming anti-reflection structures for CMOS image sensors
JP5385564B2 (en) * 2008-08-18 2014-01-08 ラピスセミコンダクタ株式会社 Semiconductor device and manufacturing method thereof
US20100289065A1 (en) 2009-05-12 2010-11-18 Pixart Imaging Incorporation Mems integrated chip with cross-area interconnection
US20100320552A1 (en) * 2009-06-19 2010-12-23 Pixart Imaging Inc. CMOS Image Sensor
TWI418024B (en) * 2009-07-06 2013-12-01 Pixart Imaging Inc Image sensor device and method for making same
KR20110077451A (en) * 2009-12-30 2011-07-07 삼성전자주식회사 Image sensor, fabricating method thereof, and device comprising the image sensor
KR101801259B1 (en) * 2010-07-21 2017-11-27 삼성전자주식회사 Light-guiding structure, Image sensor comprising the light-guiding structure, and Processor-based system comprising the image sensor
US8283754B2 (en) * 2010-08-13 2012-10-09 Taiwan Semiconductor Manufacturing Company, Ltd. Seal ring structure with metal pad
US8350934B2 (en) 2010-10-21 2013-01-08 Taiwan Semiconductor Manufacturing Co., Ltd. Color image sensor array with color crosstalk test patterns
JP5693924B2 (en) * 2010-11-10 2015-04-01 株式会社東芝 Semiconductor imaging device
FR2968879A1 (en) * 2010-12-10 2012-06-15 St Microelectronics Sa METHOD FOR CHARACTERIZING PIXELS OF AN IMAGE SENSOR
FR2969820B1 (en) * 2010-12-23 2013-09-20 St Microelectronics Sa FRONT PANEL LOW-FRONT LOW-FRONT IMAGE SENSOR
US8742309B2 (en) 2011-01-28 2014-06-03 Aptina Imaging Corporation Imagers with depth sensing capabilities
US10015471B2 (en) 2011-08-12 2018-07-03 Semiconductor Components Industries, Llc Asymmetric angular response pixels for single sensor stereo
JP5956866B2 (en) * 2011-09-01 2016-07-27 キヤノン株式会社 Solid-state imaging device
JP5943577B2 (en) 2011-10-07 2016-07-05 キヤノン株式会社 Photoelectric conversion device and imaging system
US9554115B2 (en) * 2012-02-27 2017-01-24 Semiconductor Components Industries, Llc Imaging pixels with depth sensing capabilities
US9232159B2 (en) * 2012-09-20 2016-01-05 Semiconductor Components Industries, Llc Imaging systems with crosstalk calibration pixels
JP6087107B2 (en) * 2012-10-29 2017-03-01 ルネサスエレクトロニクス株式会社 Manufacturing method of semiconductor device
US9129878B2 (en) * 2013-09-17 2015-09-08 Taiwan Semiconductor Manufacturing Co., Ltd. Mechanisms for forming backside illuminated image sensor device structure
US9425228B2 (en) * 2013-11-29 2016-08-23 Taiwan Semiconductor Manufacturing Company Limited Image sensor with reduced optical path
US9774804B2 (en) * 2013-12-13 2017-09-26 Bio-Rad Laboratories, Inc. Digital imaging with masked pixels
KR20150139255A (en) 2014-06-03 2015-12-11 에스케이하이닉스 주식회사 Semiconductor device and method of manufacturing the same
US9601502B2 (en) 2014-08-26 2017-03-21 Sandisk Technologies Llc Multiheight contact via structures for a multilevel interconnect structure
US9401309B2 (en) * 2014-08-26 2016-07-26 Sandisk Technologies Llc Multiheight contact via structures for a multilevel interconnect structure
US9479745B2 (en) * 2014-09-19 2016-10-25 Omnivision Technologies, Inc. Color filter array with reference pixel to reduce spectral crosstalk
KR102499585B1 (en) * 2015-01-13 2023-02-14 소니 세미컨덕터 솔루션즈 가부시키가이샤 Solid-state imaging device, manufacturing method thereof, and electronic apparatus
EP4290765A3 (en) 2015-09-24 2024-04-10 CubicPV Inc. System for testing photosensitive device degradation
JP6978893B2 (en) * 2017-10-27 2021-12-08 キヤノン株式会社 Photoelectric conversion device, its manufacturing method and equipment
US10734234B2 (en) 2017-12-18 2020-08-04 International Business Machines Corporation Metal cut patterning and etching to minimize interlayer dielectric layer loss
KR102535564B1 (en) * 2018-06-08 2023-05-23 삼성전자주식회사 Display panel and manufacturing method thereof
US10854658B2 (en) 2018-07-16 2020-12-01 Taiwan Semiconductor Manufacturing Company, Ltd. Image sensor with sidewall protection and method of making same
US11088037B2 (en) * 2018-08-29 2021-08-10 Taiwan Semiconductor Manufacturing Company Ltd. Semiconductor device having probe pads and seal ring
US10964741B1 (en) * 2019-09-18 2021-03-30 Omnivision Technologies, Inc. Backside illuminated sensor pixel structure
CN112838048A (en) * 2019-11-22 2021-05-25 联华电子股份有限公司 Interconnection structure and manufacturing method thereof

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5471515A (en) 1994-01-28 1995-11-28 California Institute Of Technology Active pixel sensor with intra-pixel charge transfer
US5621519A (en) * 1995-07-31 1997-04-15 Neopath, Inc. Imaging system transfer function control method and apparatus
US5651076A (en) * 1994-05-04 1997-07-22 France Telecom System for determining the bidimensional characteristic function of a continuous optical conversion member
US5708263A (en) 1995-12-27 1998-01-13 International Business Machines Corporation Photodetector array
US5818572A (en) 1996-04-24 1998-10-06 Northrop Grumman Corporation Two-dimensional modulation transfer function measurement technique
US20040233463A1 (en) * 2003-05-19 2004-11-25 Hersch Roger David Reproduction of security documents and color images with metallic inks
US6900884B2 (en) 2001-10-04 2005-05-31 Lockheed Martin Corporation Automatic measurement of the modulation transfer function of an optical system

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5621529A (en) * 1995-04-05 1997-04-15 Intelligent Automation Systems, Inc. Apparatus and method for projecting laser pattern with reduced speckle noise
KR20010059316A (en) 1999-12-30 2001-07-06 박종섭 Image sensor structure to improved photo sensitivity and method for fabricating the same
JP2002064193A (en) 2000-08-22 2002-02-28 Sony Corp Solid-state imaging device and manufacturing method thereof
JP2002110799A (en) 2000-09-27 2002-04-12 Toshiba Corp Semiconductor device and method for manufacturing the same
KR100385227B1 (en) 2001-02-12 2003-05-27 삼성전자주식회사 Semiconductor device having copper multy later circuit line and method of making the same
US7056826B2 (en) 2003-01-07 2006-06-06 Taiwan Semiconductor Manufacturing Co., Ltd. Method of forming copper interconnects
US6861686B2 (en) * 2003-01-16 2005-03-01 Samsung Electronics Co., Ltd. Structure of a CMOS image sensor and method for fabricating the same
KR20040065769A (en) 2003-01-16 2004-07-23 삼성전자주식회사 Method of manufacturing of CMOS image sensor

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5471515A (en) 1994-01-28 1995-11-28 California Institute Of Technology Active pixel sensor with intra-pixel charge transfer
US5651076A (en) * 1994-05-04 1997-07-22 France Telecom System for determining the bidimensional characteristic function of a continuous optical conversion member
US5621519A (en) * 1995-07-31 1997-04-15 Neopath, Inc. Imaging system transfer function control method and apparatus
US5708263A (en) 1995-12-27 1998-01-13 International Business Machines Corporation Photodetector array
US5818572A (en) 1996-04-24 1998-10-06 Northrop Grumman Corporation Two-dimensional modulation transfer function measurement technique
US6900884B2 (en) 2001-10-04 2005-05-31 Lockheed Martin Corporation Automatic measurement of the modulation transfer function of an optical system
US20040233463A1 (en) * 2003-05-19 2004-11-25 Hersch Roger David Reproduction of security documents and color images with metallic inks

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10267684B1 (en) 2017-04-11 2019-04-23 United States Of America As Represented By The Secretary Of The Air Force Device, system, and technique for characterizing a focal plane array modulation transfer function

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